J Winters

The Incorporation of Texture-Based Yield Loci Into Elasto-Plastic Finite Element Programs

Elasto-plastic finite elements (FE) methods are nowadays widely used to simulate complex metal forming processes. It is then useful to generate an anisotropic yield criterion from the crystallographic texture and incorporate it into such model. The theory of dual plastic potentials (one in strain rate space and one in stress space) helps to achieve this. There is however a certain danger of losing the convexity of the yield locus during this procedure. Examples of this phenomenon are given and discussed. It is furthermore explained how the yield locus can be used to generate an elasto-plastic modulus for implementation in the FE code. Finally several examples of successful applications of the anisotropic FE code to metal forming problems are given.

THE INCORPORATION OF AN ANISOTROPIC YIELD LOCUS DERIVED FROM THE CRYSTALLOGRAPHIC TEXTURE IN FE MODELLING OF FORMING

In the last decades, classical elastic finite elements (FE) methods have served as a basis for the development of more general methods that can also treat plastic deformation and are able to simulate complex metal forming processes. Most of these models still use the isotropic von Mises yield criterion and its associated flow law. It will be shown how the latter can be replaced by an anisotropic yield criterion and its associated flow law which are directly derived from the crystallographic texture of the metal that is the cause of the anisotropy. The first stage of the procedure is the determination of the orientation distribution function (ODF) that describes the texture. The next stage is the calculation of the anisotropic yield locus that corresponds to it by means of the Taylor-Bishop Hill theory. The final stage is the implementation of this yield locus in the FEM code.